Antiferroelectric Capacitors Research Articles

Exploring anti-ferroelectric thin films with high energy storage performance by moderating phase transition

Anti-ferroelectric thin films are renowned for their signature double hysteresis loops and sheds light on the distinguished energy storage capabilities of dielectric capacitors in modern electronic devices. However, anti-ferroelectric capacitors are still facing the dual challenges of low energy density and efficiency to achieve state-of-the-art performance. Their large hysteresis and sharp first-order phase transition usually results in a low energy storage efficiency and easy breakdown, severely obscuring its future application. In this study, we demonstrate that anti-ferroelectric (Pb0.97La0.02)(Zr1−xSnx)O3 epitaxial thin films exhibit enhanced energy storage performance through local structural heterogeneity to moderate the first-order phase transition by calculating the corresponding polarization as a function of switching time for the first time. The films exhibit remarkable enhanced breakdown strength (∼3.47 MV/cm, ∼5 times the value for PbZrO3) and energy storage performance. Our endeavors have culminated in the ingenious formulation of a novel strategy, namely, the postponement of polarization processes, thereby elevating the breakdown strength and total energy storage performance. This landmark achievement has unveiled a fresh vista of investigative opportunities for advancing the energy storage prowess of electric dielectrics.

Excellent energy storage performance of Nd-modified lead-free AgNbO3 ceramics via triple collaborative optimization

Lead-free Dielectric capacitors that possess high power density as well as swift charging/discharging speed are in tremendous requirement in pulse/high power fields, but the lower recovery energy density and efficiency restrict their applications. Herein, via triple collaborative optimization, we designed Nd-modified AgNbO3 antiferroelectric ceramics with excellent energy storage performance. First, Nd3+ ions are smaller than Ag+ ions, which effectively inhibits cation displacements and the tilting of oxygen octahedra, leading to an optimized phase composition, the suppressed ferroelectricity and enhanced antiferroelectricity. Second, the valence of Nd3+ ions are higher than that of Ag+ ions, which help to lower the content of oxygen vacancies. Third, the random substitution of Nd3+, extrinsic ions, cause the chemical disorder, thus dwindling the grain size. Both of the latter could boost the breakdown field. Eventually, the synchronously boosted energy density of 7.16 J/cm3 and efficiency of 72 %, together with excellent frequency stability, temperature tolerance, ultrafast charging/discharging time of 45 ns and superhigh power density of 354.2 MW/cm3, are achieved in Ag0.91Nd0.03NbO3. All these merits manifest Nd- AgNbO3 as a promising candidate for lead-free high-power energy storage devices. Our work brings forward a good reference for developing the capabilities of antiferroelectric capacitors.

Switching Dynamics and Improved Efficiency of Free‐Standing Antiferroelectric Capacitors

AbstractThe switching dynamics of antiferroelectric lead zirconate (PbZrO3) freestanding capacitors compared to their epitaxial counterparts is reported. Frequency dependence of hysteresis indicates that freestanding capacitors exhibit a lower dispersion of switching fields, lower residual polarization, and faster switching response as compared to epitaxially‐clamped capacitors. As a consequence, freestanding capacitor membranes exhibit better energy storage density and efficiency.

Antiferroelectric Ceramics for Energy-Efficient Capacitors by Theory-Guided Discovery.

Antiferroelectric ceramics, via the electric-field-induced antiferroelectric (AFE)-ferroelectric (FE) phase transitions, show great promise for high-energy-density capacitors. Yet, currently, only 70-80% energy release is found during a charge-discharge cycle. Here, for PbZrO3-based oxides, geometric nonlinear theory of martensitic phase transitions is applied (first used to guide supercompatible shape-memory alloys) to predict the reversibility of the AFE-FE transition by using density-functional theory to assess AFE/FE interfacial lattice-mismatch strain that assures ultralow electric hysteresis and extended fatigue lifetime. A good correlation of mismatch strain with electric hysteresis, hence, with energy efficiency of AFE capacitors is observed. Guided by theory, high-throughput material search is conducted and AFE compositions with a near-perfect charge-discharge energy efficiency (98.2%), i.e., near-zero hysteresis are discovered. And the fatigue life of the capacitor reaches 79.5 million charge-discharge cycles, a factor of 80 enhancement over AFE ceramics with large electric hysteresis.

Superior Energy Storage Performance in Antiferroelectric Epitaxial Thin Films via Structural Heterogeneity and Orientation Control

AbstractDielectric capacitors are desired for electronics and electrical power systems because of their fast charge–discharge speed and high‐power density. Nevertheless, dielectric capacitors typically exhibit lower energy densities in comparison to other energy storage systems like batteries or fuel cells. Among dielectrics, antiferroelectrics have shown great promise for high energy density because of their characteristic double hysteresis loops. However, current antiferroelectric capacitors still face challenges of low efficiency and low breakdown strength due to their large hysteresis, which is harmful to energy efficiency and reliability of the system. Herein, by engineering the nanoscale heterogeneity to mitigate hysteresis and controlling orientation to enhance the polarization, the exceptional energy storage performance of antiferroelectric (Pb0.97La0.02)(Zr0.55Sn0.45)O3 epitaxial thin films is demonstrated. Atomic‐resolution transmission electron microscopy and X‐ray reciprocal space mapping confirm the presence of nanoscale structural heterogeneity, characterized by fragmented antipolar nanodomains. These films exhibit remarkable energy densities, reaching up to ≈84.5 J cm−3, coupled with ultrahigh efficiencies of up to ≈98.5% and superior stability, maintaining efficiencies above 92% across a wide field range of ≈5 MV cm−1. Notably, these findings surpass the capabilities of previously reported dielectric materials, opening new avenues for advanced energy storage applications.

Excellent Energy-Storage Performance of (0.85 – x)NaNbO3–xNaSbO3–0.15(Na0.5La0.5)TiO3 Antiferroelectric Ceramics through B-Site Sb5+ Driven Phase Transition

NaNbO3-based relaxor antiferroelectric (AFE) ceramics are receiving more and more attention for high power pulse applications. A commonly used design strategy is to add complex perovskites with lower tolerance factors. Herein, a new lead-free AFE system of (0.85 - x)NaNbO3-xNaSbO3-0.15(Na0.5La0.5)TiO3 was specially designed considering the substitution of Sb5+ for Nb5+ reduces the polarizability of B-site ions but increases the tolerance factor. The formation of nanodomains with stable AFE orthorhombic R phase symmetry contributes to a slim and double-like polarization-field hysteresis loop, while the increased resistivity and activation energy as a result of sintering aids lead to an enhanced breakdown strength. Therefore, an excellent energy density Wrec ≈ 6.05 J/cm3, a high energy efficiency η ≈ 80.5%, and good charge-discharge performances (power density PD ≈ 155 MW/cm3 and discharging rate t0.9 ≈ 44.6 ns) were achieved in MnO2-doped x = 0.03 ceramics. The experimental results demonstrate that the B-site Sb5+ driven orthorhombic P-R phase transition and increased local structure disorder should provide a new strategy to design high-performance NaNbO3-based relaxor AFE capacitors.

Simulation for pulse discharge performance of antiferroelectric capacitors

The discharge performance of antiferroelectric (AFE) capacitors is complicated and difficult to simulate due to the nonlinear polarization behavior of AFE. In this work, a nonlinear model for pulsed discharge AFEs was proposed based on a combination of the Preisach model and Kirchhoff’s law. The model was driven by the data from first-order reversal curves and direct-current-bias (DC-bias) dielectric test measurements. Thus, the discharge behavior of the AFE can be studied without actual discharge experiments. Specifically, AFE discharge waveforms were calculated and evaluated for different size parameters and external circuit parameters that were conducive to compare the properties of different AFE materials. Moreover, the size effect of the capacitor on the discharge performance was discussed, which should draw the attention of researchers to prevent exaggerated conclusions. As a consequence, this method would fill the gap of AFE discharge simulation.

Heterovalent-doping-enabled atom-displacement fluctuation leads to ultrahigh energy-storage density in AgNbO3-based multilayer capacitors

Dielectric capacitors with high energy storage performance are highly desired for next-generation advanced high/pulsed power capacitors that demand miniaturization and integration. However, the poor energy-storage density that results from the low breakdown strength, has been the major challenge for practical applications of dielectric capacitors. Herein, we propose a heterovalent-doping-enabled atom-displacement fluctuation strategy for the design of low-atom-displacements regions in the antiferroelectric matrix to achieve the increase in breakdown strength and enhancement of the energy-storage density for AgNbO3-based multilayer capacitors. An ultrahigh breakdown strength ~1450 kV·cm−1 is realized in the Sm0.05Ag0.85Nb0.7Ta0.3O3 multilayer capacitors, especially with an ultrahigh Urec ~14 J·cm−3, excellent η ~ 85% and PD,max ~ 102.84 MW·cm−3, manifesting a breakthrough in the comprehensive energy storage performance for lead-free antiferroelectric capacitors. This work offers a good paradigm for improving the energy storage properties of antiferroelectric multilayer capacitors to meet the demanding requirements of advanced energy storage applications.

Ferroelectric/paraelectric superlattices for energy storage.

The polarization response of antiferroelectrics to electric fields is such that the materials can store large energy densities, which makes them promising candidates for energy storage applications in pulsed-power technologies. However, relatively few materials of this kind are known. Here, we consider ferroelectric/paraelectric superlattices as artificial electrostatically engineered antiferroelectrics. Specifically, using high-throughput second-principles calculations, we engineer PbTiO3/SrTiO3 superlattices to optimize their energy storage performance at room temperature (to maximize density and release efficiency) with respect to different design variables (layer thicknesses, epitaxial conditions, and stiffness of the dielectric layer). We obtain results competitive with the state-of-the-art antiferroelectric capacitors and reveal the mechanisms responsible for the optimal properties.

Enhancement of energy storage for electrostatic supercapacitors through built-in electric field engineering

In this study, a novel yet general strategy is proposed and demonstrated to enhance the energy storage density (ESD) of dielectric capacitors by introducing a built-in electric field in the dielectric layer, which increases the applied electric field required to polarize the dielectric. By using the top and bottom electrodes of different work functions, a built-in electric field is created in the antiferroelectric layer, which leads to an increase in the critical fields for the antiferroelectric-ferroelectric phase transition and thus the enhancement of ESD. Accordingly, the TiO2/ZrO2/TiO2 antiferroelectric capacitor with asymmetric electrodes demonstrates an ultra-high ESD of 114.5 J cm−3, which is improved by ~21% compared to the antiferroelectric capacitor without a built-in field, along with high efficiency of 76%. The achieved ESD is record-high among the HfO2/ZrO2-based lead-free antiferroelectric thin-film capacitors. The result indicates that engineering the built-in electric field can be an effective and promising approach to increasing the ESD for electrostatic supercapacitors.

Discovery of electric devil's staircase in perovskite antiferroelectric.

The devil’s staircase, describing step-like function for two competing frequencies, is well known over a wide range of dynamic systems including Huyghens’ clocks, Josephson junction, and chemical reaction. In condensed matter physics, the devil’s staircase has been observed in spatially modulated structures, such as magnetic ordering. It draws widespread attentions because it plays a crucial role in the fascinating phenomena including phase-locking behaviors, commensurate-incommensurate phase transition, and spin-valve effect. Here, we report the observation of polymorphic phase transitions consisting of several steps in PbZrO3-based system—namely, electric devil’s staircase—originated from competing ferroelectric and antiferroelectric interactions. We fully characterize a specific electric dipole configuration by decomposing this competitive interaction in terms of basic structure and modulation function. Of particular interest is that the occurrence of many degenerate electric dipole configurations in devil’s staircase enables superior energy storage performance. These observations are of great significance for exploring more substantive magnetic-electric correspondence and engineering practical high-power antiferroelectric capacitors.

Achieving ultrahigh energy-storage capability in PbZrO3-based antiferroelectric capacitors based on optimization of property parameters

An ultrahighWrecof 14.5 J cm−3and highηof 87.7% are achieved simultaneously in PbZrO3-based ceramicsviaenhancing antiferroelectricity and refining the grain size.

Better FeRAM with antiferroelectric capacitors

Better FeRAM with antiferroelectric capacitors

Evaluation of various methods for energy storage calculation in nonlinear capacitors

In the practical application of capacitors, especially in pulsed application, recoverable energy is a key parameter, which represents the ability to store energy. However, many existing evaluation methods for energy storage calculation have not been systematically implemented and comprehensively understood. In this work, four methods were applied to calculate the energy storage in linear, ferroelectric, and antiferroelectric capacitors. All methods were valid when the linear capacitor was examined. In terms of the ferroelectric capacitor, the method of equivalent parameter using DC-bias capacitance was infeasible under the high voltage owing to a massive decrease in field-dependent capacitance. As for the antiferroelectric capacitor with noticeable hysteresis, the maximum of energy storage was obtained by the method of integration of hysteresis loop, while the lower one was obtained in the fast discharge condition by the method of integration of UI (product of voltage and current). In summary, for different materials, both test conditions and calculation methods should be considered to get accurate energy storage, which best fits the working conditions.

Low electric-field-induced strain and high energy storage efficiency in (Pb,Ba,La)(Zr,Sn,Ti)O3 antiferroelectric ceramics through regulating the content of La

In addition to energy storage density (Wrec) and energy efficiency (ƞ), electrical fatigue characteristic is also an important factor affecting the performance of anti-ferroelectric (AFE) capacitors. The main impacts of electrical fatigue characteristic are strain and thermal shock. The AFE ceramic materials will undergo AFE-FE phase transition, when the applied electric field is high enough. This process is usually accompanied by huge electric-field-induced strain, which results in the fatigue phenomenon during switching cycles. Meanwhile, low ƞ will lead to heat accumulation effect during working cycles. However, researches on these aspects are very limited for AFE capacitors. In this work, the (Pb0.96-1.5xBa0.04Lax)(Zr0.65Sn0.3Ti0.05)O3 (x = 0.02, 0.03, 0.04, 0.05) AFE ceramics with low electric-field-induced strain and high ƞ are obtained by regulating the content of La. The Pb2+ creates vacancies in A-sites crystal structure by introducing La-ions can reduce the strain and difference between AFE-FE (EF) and FE-AFE (EA), thereby improving ƞ simultaneously. As a result, the PBLZST ceramics exhibit a maximum Wrec of 4.44 J cm−3 and a high ƞ of 88.8% under 170 kV cm−1 when La3+ content of x = 0.03. The Wrec and ƞ fluctuate within 4.4% and 2.5% respectively after 5000 working cycles, which demonstrates the excellent anti-fatigue characteristic related to low electric-field-induced strain (0.26%) of the sample. Besides, these ceramics have a discharge energy density (Wdis) value as high as 4.22 J cm−3 under the field 170 kV cm−1, which indicates the amount of energy that can actually be released. Those advantages illuminate the PBLZST ceramics (x = 0.03) are beneficial to the practical application of AFE capacitors.

Achieving Remarkable Amplification of Energy-Storage Density in Two-Step Sintered NaNbO3-SrTiO3 Antiferroelectric Capacitors through Dual Adjustment of Local Heterogeneity and Grain Scale.

Antiferroelectric (AFE) materials exhibit outstanding advantages against linear or ferroelectric (FE) dielectrics in high-performance energy-storage capacitors. However, their energy-storage performances are usually restricted by both extremely large hysteresis and insufficiently high driving field of the AFE-FE phase transition, which has been a longstanding issue to be overcome in the community. In this work, we report a two-step sintered 0.83NaNbO3-0.17SrTiO3 (NN-ST) lead-free relaxor AFE R-phase ceramic with high relative density of ≥95% and large spans of average grain sizes from 1.2 to 8.2 μm, strikingly achieving a giant amplification of recoverable energy-storage density (Wrec) by 176%. Analyses of permittivity-temperature curves, Raman spectrum and microstructure demonstrate that remarkably enhanced Wrec values should be ascribed to the dual adjustment of local heterogeneity (nanoscale) and grain scale (microscale), resulting in the enhanced threshold field strength for dielectric breakdown and the increased critical electric fields for the AFE-FE phase transition. A high Wrec ≈ 1.60 J/cm3, a fast discharging rate t0.9 ≈ 520 ns, large current density ∼788 A/cm2, and large power density ∼55 MW/cm3 are achieved at room temperature in the NN-ST ceramic sample with an average grain size of ∼1.2 μm. These results suggest that the multiscale structure regulation should be an efficient way for achieving enhanced energy-storage properties in NN-ST relaxor AFE ceramics through a two-step sintering technique.

Superior Energy‐Storage Capacitors with Simultaneously Giant Energy Density and Efficiency Using Nanodomain Engineered BiFeO3‐BaTiO3‐NaNbO3 Lead‐Free Bulk Ferroelectrics

AbstractDielectric capacitors are receiving a great deal of attention for advanced pulsed power owing to their high power density and quick charge/discharge rate. However, the energy density is limited and the efficiency and the thermal stability are also not ideal, which has been a longstanding obstacle to developing desirable dielectric materials. These concerns have are addressed herein by fabricating nanodomain‐engineered BiFeO3‐BaTiO3‐NaNbO3 bulk ferroelectrics, integrating a high‐spontaneous‐polarization gene, wide band gaps, and a heterogeneous nanodomain structure, generating record‐excellent comprehensive performance of giant energy‐storage density Wrec ≈8.12 J cm−3, high efficiency η ≈90% and excellent thermal stability (±10%, −50 to 250 °C) and ultrafast discharge rate (t0.9 < 100 ns). Significantly enhanced dielectric breakdown strength of BiFeO3‐based solid solutions is mainly attributed to the substitution of NaNbO3, which provides an increased band gap, refined grain size, and increased resistivity. The formation of nanoscale domains as evidenced by piezoresponse force microscopy and transmission electron microscopy enables nearly hysteresis‐free polarization‐field response and temperature‐insensitive dielectric response. In comparison with antiferroelectric capacitors, the current work provides a new solution to successfully design next‐generation pulsed power capacitors by fully utilizing relaxor ferroelectrics in energy‐storage efficiency and thermal stability.

Flexible antiferroelectric thick film deposited on nickel foils for high energy‐storage capacitor

AbstractFlexible antiferroelectric (AFE) Pb0.94La0.04Zr0.97Ti0.03O3 (PLZT) thick‐film capacitors were fabricated on nickel foil substrates using sol‐gel method. The thick PLZT film shows pure perovskite phase with dense microstructure. The discharge energy‐storage properties of the thick PLZT film are directly evaluated by the resistance‐inductance‐capacitance (RLC) circuit. The maximum value of the discharge energy‐storage density (Wdis) is 15.8 J/cm3 at 1400 kV/cm and 90% of the corresponding energy is released in a short time of about 250 ns. In addition, the Wdis and discharge time could be adjusted by the bent radius of the film, which provides a simple and feasible solution for the regulation of the electrical performance. Furthermore, the flexible AFE film exhibits good mechanical properties under cycling tests with bending radii down to 2.5 mm and 1500 rounds. This work shows a critical significance in fabricating flexible AFE capacitors for application in modern electronics and electrical power systems.

Effect of dielectric response on discharge properties of PLZST antiferroelectric ceramics

Dielectric capacitors play a key role in revolutionizing modern electronic and electrical devices. Among these capacitors, anti-ferroelectric (AFE) capacitors receive much attention due to nonlinear dielectric properties and high-power output. (Pb0.89Ba0.08La0.02)(Zr0.50Sn0.40Ti0.10)O3 AFE ceramic with excellent dielectric nonlinearity was prepared via the solid state reaction, and the influence of dielectric response on discharge properties of AFE ceramics was studied. The results showed that dielectric constant (e) increased first and then decreased with electric field increasing and presented two peaks at 11.4 kV/cm and 16.9 kV/cm, corresponding to AFE–ferroelectric (FE) phase transition. Below 16.9 kV/cm, or before the AFE–FE phase transition, the discharge current increased. Beyond 16.9 kV/cm, or after AFE–FE phase transition, the current raised weakly and reached about 120A at 50 kV/cm, and it was hard to continue to increase the current after AFE–FE phase transitions. Therefore, dielectric response in AFEs had a great influence on the discharge performance. The results provided a simple method to select the appropriate working electric field for the practical application of AFEs capacitors.

Mechanical self-confinement to enhance energy storage density of antiferroelectric capacitors

The energy storage density of electrical capacitors utilizing antiferroelectric compositions Pb0.99Nb0.02[(Zr0.57Sn0.43)1−yTiy]0.98O3 as dielectrics is measured at a series of temperatures in a series of dielectric compositions with and without self-confinement. Under the applied electric field of 70 kV/cm, a maximum energy density of 1.3 J/cm3 is achieved. The mechanical self-confinement was introduced by partially electroding the central portion of the dielectric ceramic disk. A phase-field model was developed and it confirms the presence of compressive stresses ∼30 MPa in the electroded portion of the dielectric disk and the contribution to the increased energy density from the mechanical confinement.